RAN has D-RAN, X-RAN, C-RAN, and now O-RAN.
RAN is the base station, which is the network. Before the advent of the 5G era, a base station (RAN) was composed of three parts, an antenna, RRU (remote radio unit), and BBU (baseband processing unit). RRU is used to transmit and receive signals, and BBU is used to process signaling messages.
In the 1G and 2G eras, the BBU, RRU, power supply unit, and other equipment are placed in a cabinet, which is very bloated.
In the 3G era, a distributed base station was proposed. That is, the BBU and the RRU are separated, and the RRU can even be hung under the antenna, and it does not need to be placed in the same cabinet as the BBU. This is the so-called D-RAN (Distributed Radio Access Network). With the development of technology (a big reason is that the maintenance cost of operators is too high), C-RAN came into being.
What is C-RAN?
It is Centralized RAN, or Cloud-RAN, which means centralized wireless access. The solution of separating BBU and RRU is still adopted, but the RRU is infinitely close to the antenna, which greatly reduces the attenuation through the feeder (the connection between the antenna and the RRU);
At the same time, the BBU is migrated and concentrated in the CO (central computer room) to form a BBU baseband pool; and The CO and RRU are connected through the fronthaul network. This is very conducive to the collaborative work between cells, reduces the attenuation caused during transmission, and saves costs.
Overseas operators are also constantly exploring more advanced network architectures. In 2016, AT&T led many overseas operators to establish the x-RAN alliance, with the goal of replacing traditional hardware-based RAN with open and replaceable standardized equipment. The alliance focuses on three aspects: coupling the RAN control plane with the user plane, building a modular eNodeB software stack using COTS hardware, and opening south and north interfaces.
X-RAN and C-RAN are generally regarded as the predecessors of O-RAN.
What is O-RAN?
A radio access network is part of a mobile telecommunication system. It implements radio access technology. Conceptually, it resides between a device such as a mobile phone, a computer, or any remotely controlled machine and provides a connection with its core network.
In June 2018, the O-RAN Alliance was formally established, jointly initiated by 12 operators including China Mobile, AT&T, Deutsche Telekom, NTT DOCOMO of Japan, and Orange of France. The O-RAN alliance expands on the work results and goals of the existing C-RAN alliance and promotes the evolution of the radio access network in a more open and intelligent direction.
But why set up the O-RAN alliance?
How O-RAN was born?
Wireless network construction has always been the most important part of the overall network cost (TCO) of operators, roughly accounting for 60% to 70%. Most operators have just experienced huge investments in 4G networks, they will face the pressure of investment and construction of 5G networks.
A 5G network is different from a 4G network. 5G network has fast speed, large bandwidth, and a high-frequency band. In other words, the penetration of the 5G network will be far worse than that of the 4G network. The original 4G network requires only 1 base station to cover a certain area, while 5G network coverage requires 5 base stations. In this way, China will need millions or even tens of millions of 5G small base stations in the future.
At the same time, the 5G network is a network that operators must invest in. Large-scale network construction will inevitably bring huge costs. At this time, it is necessary to introduce new technologies and new solutions to reduce the difficulty of construction and reduce wireless network investment through program innovation.
In the context of the slowdown in wireless Internet traffic revenue growth and the decline in voice revenue, vertical industries are the blue ocean market that operators must enter. Expanding the profitability of operators will be the primary task of 5G networks.
New base station businesses in vertical industries mean more diverse business types, more complex network management, more efficient resource management solutions, and more flexible network architectures are needed to facilitate business innovation.
In this context, the O-RAN industry alliance led by operators came into being and proposed two core visions of openness and intelligence.
The core of O-RAN is standardization and open source
O-RAN ALLIANCE is Transforming the Radio Access Networks Industry Towards Open, Intelligent, Virtualized, and Fully Interoperable RAN. The ORAN Alliance is led and initiated by operators and has three key principles.
The first principle is to guide the evolution of the industry. The first is to open interfaces to support the interoperability of devices from different manufacturers; the second is to build a wireless access network through virtualization to realize an intelligent wireless network based on big data.
The second principle is to actively and fully utilize common platforms and reduce dependence on private platforms.
The third principle is to formulate and promote standardized definitions of interfaces and related APIs and explore open-source solutions.
O-RAN is promoting the following four directions: network intelligence, interface openness, hardware generalization, and software open source. The hardware that was originally a black box has now all been transformed into general standardized products, and the software code in it has also become open source.
This may mean that in the future, no matter how large the number of equipment from a single manufacturer on an existing network is, it is not irreplaceable; sellers do not need to package and purchase software and hardware products from the same manufacturer but make full use of common platforms and reduce the need for private platforms. The development and promotion of interface and related API standardization definitions and the exploration of open-source solutions also mean that standardization will become a trend.
With the opening of generalized hardware, the hardware will be generalized after the decoupling of network functions from software and hardware, and the independence of operators will be higher, instead of being always swayed by equipment vendors as they are now. Traditional equipment vendors will face major changes, and some Internet companies, software vendors, and IT vendors may become new players in the market.
In fact, some IT vendors have already begun to watch. At the MWC 2019 Barcelona exhibition, Lenovo and China Mobile jointly showcased the world’s first 5G O-RAN product. This product realized the cross-node, multi-virtual machine, and all-software 5G CU/DU device cloudification solution for the first time in the industry.
The joint demonstration not only verified that Lenovo’s IT infrastructure solutions can effectively support the cloudification needs of wireless networks, but it is also a useful attempt for operators to develop base station equipment in depth. Facing the evolution of intelligent and open wireless networks in the future, the integration of wireless network R&D and operation is an important direction, and more industry partners are welcome to participate.
Lenovo Group, together with China Mobile Research Institute and partners, released the world’s first open-edge hardware acceleration platform for 5G. As a veteran IT manufacturer, Lenovo has also begun to make an all-out effort to 5G and quickly seize the O-RAN market.
Challenges and Prospects of O-RAN
What O-RAN wants to solve is the problem of cost and efficiency. How to achieve a balance between versatility, energy efficiency ratio, and overall cost is the core key issue for the research and development of general base station reference designs.
At present, Ericsson, Nokia, ZTE, and Lenovo have all joined the O-RAN alliance, but Huawei has no plan to join the O-RAN alliance. Huawei prefers another vertical integration solution. The interface can be optimized according to its architecture. The two options are like two ends of the balance. On the one hand, operators are embracing openness with universal standards, and on the other is the black box problem of traditional telecommunications equipment.
At present, the membership of the O-RAN Alliance has expanded to more than 60. O-RAN will make every effort to accelerate, gather more forces for the development of next-generation wireless communication networks, promote industrial prosperity, and make a vital contribution to the deployment of 5G in the next few years.
Now that O-RAN has gradually become the consensus of global operators, AT&T promises to virtualize 75% of core network functions in 2020 and 65% in 2018. In the next few years, only standardized routers plan to deploy 60,000 units. A securities company once predicted that China’s 5G investment scale will reach 1.2 trillion yuan, of which base station equipment and transmission equipment will account for 45% and 22% respectively. From this point of view, the development prospects of standard equipment can be expected.
The industry reform surrounding O-RAN may be a protracted battle. The technical concepts and standards advocated by O-RAN have their advanced nature, but the industry is often not determined by a single factor. 5G is an additional driving force for open technologies such as O-RAN, and the determination of operators to invest will determine the final outcome of open-source communications.
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